The overall project objective is to carry forward a collaborative program of tropical parasitic disease research on several basic problems which underlie the major health priorities of the Republic of Sudan. The solutions we seek should permit inferences to be drawn which are of value to those involved in the characterization, prevention, treatmen and control of parasitic diseases elsewhere in the tropics. Four widespread and important human parasitoses will be addressed: schistosomiasis, malaria, leishmaniasis, and onchocerciasis. Our research on schistosomiasis will focus on the efficacy, pharmacokinetics, and modes of action of two emerging antischistosomal agents of potential value in mass and individual therapy of both S. mansoni and S. haematobium infections in the future. Dietary interactions which may influence eficacy, tolerance and practical acceptance will be emphasized. The goal of the malaria project is to evaluate the relationship between functional immunity to P. falciparum and in vitro assays of immune responsiveness. Advantage will be taken of the opportunity to assess both cellular and humoral mechanisms in terms of their influences on survival, growth and development of the parasite in in vitro cultures, and the results correlated with longitudinal characterization of the acquired resistance status of Sudanese in malaria endemic areas. The immunological basis for the distinct clinical syndromes of leishmaniasis in eastern Sudan will be determined and the biological traits and diagnostic characteristcs of major endemic strains of L. donovani identified. Parallel objectives will be pursued for the disease syndromes caused by Onchocerca volvulus in several of the major foci of onchocerciasis throughout Sudan. Particular emphasis will be placed on the development of capability for long-term clinical parasitological and immunological evaluation of new therapies for river blindness. Sustained involvement of Sudanese administrators, professionals, and technicians throughout this program will ensure enhancement of national research capacity for the future, and the research results should contribute to improvements in health care for the affected human populations throughout the country.